A combination of Thanksgiving and Christmas. Also known as The Holiday Season. ThanXmas is a span of time beginning around Halloween when retailers' Holiday campaigns' are in full swing and ending around the first week of the new year after the last Holiday sale concludes. Typically ThanXmas is disengaged from specific traditional or religious customs in that those who celebrate tend to forget the actual reason for the Holidays that are observed. ThanXmas or The Holiday Season is a result of advertising campaigns by major retailers that skew the meaning of the Holidays as to make the celebrations appropriate for people of all religions and ethnicities so they, the retailers, can sell more shit. A great example is "The Gift of Giving." Complete bullshit, doesn't even make sense.

Robert: So many people don't even realize that Halloween was a day of religious festivities in various northern European Pagan traditions, Thanksgiving Day is a celebration of the deliverance of the English settlers by Native Americans after the brutal winter at Plymouth, Massachusetts, Hanukkah is about the eternal flame at The Jewish Temple in Jerusalem and Christmas is the observed birthday of the Son of God, Jesus Christ.
Thomas: Dude, shut the fuck up, you're ruining my ThanXmas, I'm trying to get into the Holiday spirit.

It is very clever because the shortening of Thanks is "Thanx", like how the youngsters do the textings and whatnot, while, at the same time, the "x"is the first letter of "X-mas".

It's February and my manager is already hounding me to submit my time-off requests for the Thanx-mas season, which is over 9 months away. I could literally conceive and become the father of an un-planned child during that time-frame, and he wants to know what my holiday plans are.